The heavily briefed energy price cap was missing from the Conservative manifesto: Getty

Theresa May is expected to water down promises for an energy price cap, with the heavily briefed promise failing to appear in the party’s manifesto.

The manifesto instead promised a more wide-ranging “independent review” into the country’s rising energy costs.

Earlier this month, Theresa May had promised a cap on energy prices which was estimated to save 17 million customers £100 or more, which she described as “ “capping energy prices to support working families.”

But while the manifesto outlined various new plans, including boosting the fracking industry, it stopped short of explicitly mentioning the cap on prices.

“We want to make sure that the cost of energy in Britain is internationally competitive, both for businesses and households,” it said.

“Alongside giving individuals greater control over their energy bills and protecting customers from unfair bills, we will help them to save energy.”

But encouraging people to save energy, via other plans such as a drive to improve energy efficiency in homes, is very different from reducing the upfront cost of power.

A Conservative spokesman said: "There has been absolutely no watering down of our plans to cap energy prices and to suggest otherwise is simply wrong."

The main financial market reaction to yesterday’s manifesto was a 4 per cent rise in the share price of Centrica, the company that owns British Gas. Share prices of the big energy companies had previously fallen in response to the government’s more hardline plans.